Re: [PATCH 04/10] mm: replace get_user_pages_locked() write/force parameters with gup_flags
On Thu 13-10-16 01:20:14, Lorenzo Stoakes wrote: > This patch removes the write and force parameters from get_user_pages_locked() > and replaces them with a gup_flags parameter to make the use of FOLL_FORCE > explicit in callers as use of this flag can result in surprising behaviour > (and > hence bugs) within the mm subsystem. > > Signed-off-by: Lorenzo Stoakes After our discussion the patch looks good to me. You can add: Reviewed-by: Jan Kara Honza -- Jan Kara SUSE Labs, CR
Re: [PATCH 04/10] mm: replace get_user_pages_locked() write/force parameters with gup_flags
On Tue 18-10-16 14:56:09, Lorenzo Stoakes wrote: > On Tue, Oct 18, 2016 at 02:54:25PM +0200, Jan Kara wrote: > > > @@ -1282,7 +1282,7 @@ long get_user_pages(unsigned long start, unsigned > > > long nr_pages, > > > int write, int force, struct page **pages, > > > struct vm_area_struct **vmas); > > > long get_user_pages_locked(unsigned long start, unsigned long nr_pages, > > > - int write, int force, struct page **pages, int *locked); > > > + unsigned int gup_flags, struct page **pages, int *locked); > > > > Hum, the prototype is inconsistent with e.g. __get_user_pages_unlocked() > > where gup_flags come after **pages argument. Actually it makes more sense > > to have it before **pages so that input arguments come first and output > > arguments second but I don't care that much. But it definitely should be > > consistent... > > It was difficult to decide quite how to arrange parameters as there was > inconsitency with regards to parameter ordering already - for example > __get_user_pages() places its flags argument before pages whereas, as you > note, > __get_user_pages_unlocked() puts them afterwards. > > I ended up compromising by trying to match the existing ordering of the > function > as much as I could by replacing write, force pairs with gup_flags in the same > location (with the exception of get_user_pages_unlocked() which I felt should > match __get_user_pages_unlocked() in signature) or if there was already a > gup_flags parameter as in the case of __get_user_pages_unlocked() I simply > removed the write, force pair and left the flags as the last parameter. > > I am happy to rearrange parameters as needed, however I am not sure if it'd be > worthwhile for me to do so (I am keen to try to avoid adding too much noise > here > :) > > If we were to rearrange parameters for consistency I'd suggest adjusting > __get_user_pages_unlocked() to put gup_flags before pages and do the same with > get_user_pages_unlocked(), let me know what you think. Yeah, ok. If the inconsistency is already there, just leave it for now. Honza -- Jan Kara SUSE Labs, CR
Re: [PATCH 04/10] mm: replace get_user_pages_locked() write/force parameters with gup_flags
On Tue, Oct 18, 2016 at 02:54:25PM +0200, Jan Kara wrote: > > @@ -1282,7 +1282,7 @@ long get_user_pages(unsigned long start, unsigned > > long nr_pages, > > int write, int force, struct page **pages, > > struct vm_area_struct **vmas); > > long get_user_pages_locked(unsigned long start, unsigned long nr_pages, > > - int write, int force, struct page **pages, int *locked); > > + unsigned int gup_flags, struct page **pages, int *locked); > > Hum, the prototype is inconsistent with e.g. __get_user_pages_unlocked() > where gup_flags come after **pages argument. Actually it makes more sense > to have it before **pages so that input arguments come first and output > arguments second but I don't care that much. But it definitely should be > consistent... It was difficult to decide quite how to arrange parameters as there was inconsitency with regards to parameter ordering already - for example __get_user_pages() places its flags argument before pages whereas, as you note, __get_user_pages_unlocked() puts them afterwards. I ended up compromising by trying to match the existing ordering of the function as much as I could by replacing write, force pairs with gup_flags in the same location (with the exception of get_user_pages_unlocked() which I felt should match __get_user_pages_unlocked() in signature) or if there was already a gup_flags parameter as in the case of __get_user_pages_unlocked() I simply removed the write, force pair and left the flags as the last parameter. I am happy to rearrange parameters as needed, however I am not sure if it'd be worthwhile for me to do so (I am keen to try to avoid adding too much noise here :) If we were to rearrange parameters for consistency I'd suggest adjusting __get_user_pages_unlocked() to put gup_flags before pages and do the same with get_user_pages_unlocked(), let me know what you think.
Re: [PATCH 04/10] mm: replace get_user_pages_locked() write/force parameters with gup_flags
On Thu 13-10-16 01:20:14, Lorenzo Stoakes wrote: > This patch removes the write and force parameters from get_user_pages_locked() > and replaces them with a gup_flags parameter to make the use of FOLL_FORCE > explicit in callers as use of this flag can result in surprising behaviour > (and > hence bugs) within the mm subsystem. > > Signed-off-by: Lorenzo Stoakes > --- > include/linux/mm.h | 2 +- > mm/frame_vector.c | 8 +++- > mm/gup.c | 12 +++- > mm/nommu.c | 5 - > 4 files changed, 15 insertions(+), 12 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 6adc4bc..27ab538 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1282,7 +1282,7 @@ long get_user_pages(unsigned long start, unsigned long > nr_pages, > int write, int force, struct page **pages, > struct vm_area_struct **vmas); > long get_user_pages_locked(unsigned long start, unsigned long nr_pages, > - int write, int force, struct page **pages, int *locked); > + unsigned int gup_flags, struct page **pages, int *locked); Hum, the prototype is inconsistent with e.g. __get_user_pages_unlocked() where gup_flags come after **pages argument. Actually it makes more sense to have it before **pages so that input arguments come first and output arguments second but I don't care that much. But it definitely should be consistent... Honza -- Jan Kara SUSE Labs, CR
